The source of a power MOSFET (metal oxide semiconductor field effect transistor) is typically shorted to the oppositely doped body using the source metallization to suppress parasitic NPN action in the transistor. An integrated body diode connected anti-parallel with the transistor is formed by shorting the source to the body. During commutation from forward conduction to the off-state, the diode displays a transient reverse current that far exceeds the maximum rated blocking current. This reverse current is called reverse recovery current and its time integral is the recovered charge (Qrr).
Commutation measurement is an important application measurement for power MOSFETs and involves measuring the following parameters related to the reverse recovery characteristics of a transistor: reverse recovery charge; reverse recovery time; rising time; falling time; maximum reverse recovery current; maximum reverse recovery voltage; voltage rising speed (dv/dt); and softness. The test hardware must have very high current rising (di/dt) capability to effectively measure commutation. The di/dt capability of conventional commutation measurement test hardware systems is about 700 A/μs or less which is often not sufficient to meet customer requirements at different temperatures under high di/dt.